The Darkest Path.
In the warriors series, the cats that join Starclan are those who die and have followed the warrior code, and served their clan faithfully.
Mosskit did join Starclan as you will learn (if you haven't already) in Warriors Field Guide: Secrets of the clans. He died while Bluestar was bringing Mosskit, Stonekit, and Mistykit to their father: Oakheart of riverclan.
Firestar will join StarClan when he loses his last life. yes firestar join's starclan after the battle in fading echoes he had one life then he died of Greencough so brambleclaw becomes bramblestar also Jayfeather visits StarClan and the Place of No Stars, when he goes to the Moonpool and sees the faint outline of Firestar. Yellowfang explains he will be able to see and hear when he fully dies, and they see the faint outlines of other cats, "dead and long forgotten". that's what she said to jayfether so finally he could become a warrior but he needs a apprentice.
So far in in the entire series, Firestar has not joined Starclan, In Omen of Stars (the 4th book section) he might die, but no one really knows who many live he has left. But all that may be answered somewhere later in the series.
Yes. Actually, according to Erin Hunter, Sandstorm's mother was Brindleface.
Yes. He did. He is a resident of StarClan
In "Warriors: A Dangerous Path," the cats that die are Stonefur, Runningwind, Whitestorm, Lionheart, and Brindleface. Stonefur is killed by Blackfoot during the 'Great Battle'. Runningwind, Whitestorm, and Lionheart die during the 'Great Battle', while Brindleface is killed by Tigerstar's dogs.
In the Warriors book series, it is believed that noble Clan cats go to StarClan when they die. StarClan is a spiritual realm where deceased Clan cats reside, watching over their living relatives and providing guidance through signs and dreams.
According to Erin Hunter, only the evil cats that believed in StarClan go to Place of No Stars, when they die. Scourge and Bone did not believe in StarClan.
(Actually, Hollyleaf didn't die. Well if she did die, everybody should know that she will go to Dark Forest.)It's unsure whether hollyleaf went to starclan or not. there has been no evidence that she is in the Dark Forest or Starclan.
*SPOILER* He will fully die in the next book to be released, The Last Hope. What I mean by fully is when he became clan leader he was granted 9 lives from StarClan, so he will die 9 times before his full death.
Starclan has no camp. Its true. StarClan has NO camp. Why? Because StarClan is a Clan of dead cats. There are no leaders or a camp. I mean if they all had those things, it would be totally confusing right? If like 2 or more leaders died and went to StarClan and it was like a normal clan, how was it going to work out? There can't more 2 or more StarClans. So StarClan is just a place where every GOOD cat goes when they die. They look and watch their loved ones, visit them in dreams, send prophecies. And that is why StarClan has no camp.